The present illustrative embodiments are related to methods and systems for providing a watermark in a printed version of an image. The systems and methods provide at least one augmenting or additional colorant in addition to the typical customary, common or ordinary subtractive primary colorants (i.e., cyan, yellow, magenta and/or black primary colorants). The additional or augmenting colorants are atypical, uncommon or extended set colorants (i.e., not full load cyan, magenta, yellow or black). Increasing the number of available colorants increases the number of colors for which alternative colorant recipes can be found. Watermark information is used to select between alternate colorant recipes or colorant selection functions. For the most part, embodiments will be described in terms of systems that include the four subtractive primary colorants. However, embodiments can readily be adapted for systems that use other or fewer primary colorants. For example, an embodiment adapted for black and white imaging systems can include a means for providing a low-load black or gray colorant in addition to a customary or common subtractive black colorant.
There are many reasons for hiding data or providing a watermark in an image. Watermarks or hidden information are provided in printed documents to provide a method for authenticating a document. For example, many bank checks and/or negotiable securities include watermarks in order to combat fraud and counterfeiting. Additionally, watermarks are provided in images as a means for covert communication. Watermarking can also be used to provide information regarding the watermarked image or document.
For example, U.S. Pat. No. 7,070,252 B2 to de Queiroz, et al., which issued Jul. 4, 2006, describes selecting between gray color replacement (GCR) techniques to encode rendering hints or tags, for guiding the reproduction of copies of the image, in printed versions of the image.
Proportional amounts of the subtractive primary colorants, cyan, magenta and yellow, combine to absorb all of the wavelengths of the visible spectrum. Accordingly, when a colorant recipe for producing a color calls for respective amounts of cyan, magenta and yellow colorants, some fraction of those respective amounts can be replaced with a respective proportional amount of black colorant. Taking advantage of this phenomenon is referred to as gray component replacement (GCR). When this phenomenon is fully taken advantage of, i.e., when the entire neutral, gray or black component of a combination of cyan, magenta and yellow colorants is replaced with a black colorant, the strategy is referred to as 100% GCR. When none of the respective amounts of cyan, magenta and yellow colorants are replaced with black colorant, the strategy is referred to as 0% GCR. Fractional GCR strategies (e.g., 25%, 50%, 75%) may also be applied. Accordingly, where a color includes a neutral or gray component, and as described by de Queiroz, et al., the color can be rendered according to any selected GCR strategy. Where the GCR strategy is selected according to spatially varying watermark information, the varying GCR selections encode the watermark information in a rendered version of the image.
However, encoding by GCR strategy selection is limited to those portions of an image that have colors that include a neutral component.
There has been a desire for systems and methods for providing encoded information or watermarks that can be applied to portions of an image that do not include useful neutral components.